Definitions for "Thoroughbass"
C17 and C18 term denoting the basso continuo part or the performance practices associated with the playing of that part.
"A corruption of 'through bass' (in English) in the sense of one which is continuous, hence an approximate translation of Basso continuo. As such, it specifically relates to a characteristic feature of the new style of composition which emerged ca. 1600 replacing the intermittent bass lines of earlier music. The thorough-bass part was usually supplemented with figures, hence the common expression "Figured bass" by which it is also known, indicating the accompanying harmonies which were filled out or "realised" on a keyboard instrument (or lute) in extempore fashion ... together with additional support from other bass (wind and/or string) instruments" (IAML) (Thorin)